1. Technical Field
The present disclosure relates to a variable flow valve mechanism for opening and closing an opening portion of a variable gas flow passage for adjusting a flow rate of an exhaust gas supplied to a turbine wheel side in a turbocharger such as a turbocharger for a vehicle and a turbocharger.
2. Description of the Related Art
As a measure for suppressing an excessive rise of a turbocharging pressure by a turbocharger for a vehicle, a bypass passage is usually formed inside a turbine housing in the turbocharger for a vehicle. A part of an exhaust gas flows through this bypass passage and bypasses the turbine wheel. Furthermore, a waste gate valve for opening and closing an opening portion of the bypass passage is provided at an appropriate position of the turbine housing. Here, the bypass passage is one of a variable gas flow passage for adjusting a flow rate of the exhaust gas supplied to the turbine wheel side, and the waste gate valve is one of a variable flow valve mechanism for opening and closing an opening portion of the variable gas flow passage.
The waste gate valve includes a stem (rotating shaft) rotatably supported by the turbine housing, a valve capable of abutting on and being separated from a valve seat on the opening portion side in the bypass passage, and a mounting member for connecting the stem with the valve. The stem is rotatably supported to a forward direction and to a backward direction in a support hole penetrated and formed in an outer wall of the turbine housing. A base end portion (one end portion) of the stem protrudes outside the turbine housing. Furthermore, a base end portion of the mounting member is integrally connected to a distal end portion of the stem. A valve is provided at a distal end portion of the mounting member. The valve is capable of abutting on and being separated from the valve seat on the opening portion side in the bypass passage. Moreover, a base end portion (one end portion) of a link member is integrally connected to the base end portion of the stem. When the link member swings in the forward direction or in the backward direction around a shaft center of the stem, the valve swings in the forward direction or in the backward direction (in an opening direction or in a closing direction) via the stem and the mounting member.
An actuator is disposed on an outer wall of a compressor housing in the turbocharger for a vehicle. The actuator swings the link member around a shaft center of the stem. In addition, the actuator includes an actuating rod movable in an axial direction thereof (an axial direction of the actuating rod, in other words, an axial direction of the actuator). A distal end portion of the actuating rod is rotatably connected to a distal end portion (the other end portion) of the link member. When the turbocharging pressure reaches a set pressure, the drive of the actuator makes the actuating rod move to one side of the axial direction thereof (the axial direction of the actuating rod) to thereby swing the link member in the forward direction. When the turbocharging pressure becomes less than the set pressure after the opening portion of the bypass passage is opened, the drive of the actuator makes the actuating rod move to the other side in the axial direction thereof to thereby swing the link member in the backward direction.
Note that a technology relating to the present disclosure is shown in Japanese Patent Application Laid-Open Publication Nos. 2009-236088 and 2008-101589.